bootstrap: clean up a few clippy findings

remove useless format!()s
remove redundant field names in a few struct initializations
pass slice instead of a vector to a function
use is_empty() instead of comparisons to .len()

No functional change intended.

Author: matthiaskrgr

Diff for: src/bootstrap/compile.rs

@@ -69,7 +69,7 @@ impl Step for Std {
         if builder.config.keep_stage.contains(&compiler.stage) {
             builder.info("Warning: Using a potentially old libstd. This may not behave well.");
             builder.ensure(StdLink {
-                compiler: compiler,
+                compiler,
                 target_compiler: compiler,
                 target,
             });
@@ -358,7 +358,7 @@ impl Step for Test {
         if builder.config.keep_stage.contains(&compiler.stage) {
             builder.info("Warning: Using a potentially old libtest. This may not behave well.");
             builder.ensure(TestLink {
-                compiler: compiler,
+                compiler,
                 target_compiler: compiler,
                 target,
             });
@@ -480,7 +480,7 @@ impl Step for Rustc {
         if builder.config.keep_stage.contains(&compiler.stage) {
             builder.info("Warning: Using a potentially old librustc. This may not behave well.");
             builder.ensure(RustcLink {
-                compiler: compiler,
+                compiler,
                 target_compiler: compiler,
                 target,
             });
@@ -816,8 +816,8 @@ fn copy_codegen_backends_to_sysroot(builder: &Builder,
         let filename = file.file_name().unwrap().to_str().unwrap();
         // change `librustc_codegen_llvm-xxxxxx.so` to `librustc_codegen_llvm-llvm.so`
         let target_filename = {
-            let dash = filename.find("-").unwrap();
-            let dot = filename.find(".").unwrap();
+            let dash = filename.find('-').unwrap();
+            let dot = filename.find('.').unwrap();
             format!("{}-{}{}",
                     &filename[..dash],
                     backend,

Diff for: src/bootstrap/flags.rs

@@ -93,8 +93,7 @@ impl Default for Subcommand {
 impl Flags {
     pub fn parse(args: &[String]) -> Flags {
         let mut extra_help = String::new();
-        let mut subcommand_help = format!(
-            "\
+        let mut subcommand_help = String::from("\
 Usage: x.py <subcommand> [options] [<paths>...]
 
 Subcommands:
@@ -365,8 +364,8 @@ Arguments:
         }
 
         let cmd = match subcommand.as_str() {
-            "build" => Subcommand::Build { paths: paths },
-            "check" => Subcommand::Check { paths: paths },
+            "build" => Subcommand::Build { paths },
+            "check" => Subcommand::Check { paths },
             "test" => Subcommand::Test {
                 paths,
                 bless: matches.opt_present("bless"),
@@ -386,9 +385,9 @@ Arguments:
                 paths,
                 test_args: matches.opt_strs("test-args"),
             },
-            "doc" => Subcommand::Doc { paths: paths },
+            "doc" => Subcommand::Doc { paths },
             "clean" => {
-                if paths.len() > 0 {
+                if !paths.is_empty() {
                     println!("\nclean does not take a path argument\n");
                     usage(1, &opts, &subcommand_help, &extra_help);
                 }
@@ -413,19 +412,19 @@ Arguments:
             keep_stage: matches.opt_strs("keep-stage")
                 .into_iter().map(|j| j.parse().unwrap())
                 .collect(),
-            host: split(matches.opt_strs("host"))
+            host: split(&matches.opt_strs("host"))
                 .into_iter()
                 .map(|x| INTERNER.intern_string(x))
                 .collect::<Vec<_>>(),
-            target: split(matches.opt_strs("target"))
+            target: split(&matches.opt_strs("target"))
                 .into_iter()
                 .map(|x| INTERNER.intern_string(x))
                 .collect::<Vec<_>>(),
             config: cfg_file,
             jobs: matches.opt_str("jobs").map(|j| j.parse().unwrap()),
             cmd,
             incremental: matches.opt_present("incremental"),
-            exclude: split(matches.opt_strs("exclude"))
+            exclude: split(&matches.opt_strs("exclude"))
                 .into_iter()
                 .map(|p| p.into())
                 .collect::<Vec<_>>(),
@@ -488,7 +487,7 @@ impl Subcommand {
     }
 }
 
-fn split(s: Vec<String>) -> Vec<String> {
+fn split(s: &[String]) -> Vec<String> {
     s.iter()
         .flat_map(|s| s.split(','))
         .map(|s| s.to_string())

Diff for: src/bootstrap/lib.rs

@@ -768,7 +768,7 @@ impl Build {
                 let sha = self.rust_info.sha().expect("failed to find sha");
                 format!("/rustc/{}", sha)
             }
-            GitRepo::Llvm => format!("/rustc/llvm"),
+            GitRepo::Llvm => String::from("/rustc/llvm"),
         };
         Some(format!("{}={}", self.src.display(), path))
     }
@@ -783,7 +783,7 @@ impl Build {
     fn cflags(&self, target: Interned<String>, which: GitRepo) -> Vec<String> {
         // Filter out -O and /O (the optimization flags) that we picked up from
         // cc-rs because the build scripts will determine that for themselves.
-        let mut base = self.cc[&target].args().iter()
+        let mut base: Vec<String> = self.cc[&target].args().iter()
                            .map(|s| s.to_string_lossy().into_owned())
                            .filter(|s| !s.starts_with("-O") && !s.starts_with("/O"))
                            .collect::<Vec<_>>();
@@ -806,10 +806,10 @@ impl Build {
         if let Some(map) = self.debuginfo_map(which) {
         let cc = self.cc(target);
             if cc.ends_with("clang") || cc.ends_with("gcc") {
-                base.push(format!("-fdebug-prefix-map={}", map).into());
+                base.push(format!("-fdebug-prefix-map={}", map));
             } else if cc.ends_with("clang-cl.exe") {
                 base.push("-Xclang".into());
-                base.push(format!("-fdebug-prefix-map={}", map).into());
+                base.push(format!("-fdebug-prefix-map={}", map));
             }
         }
         base

Diff for: src/bootstrap/sanity.rs

@@ -74,7 +74,7 @@ pub fn check(build: &mut Build) {
     // one is present as part of the PATH then that can lead to the system
     // being unable to identify the files properly. See
     // https://github.com/rust-lang/rust/issues/34959 for more details.
-    if cfg!(windows) && path.to_string_lossy().contains("\"") {
+    if cfg!(windows) && path.to_string_lossy().contains('\"') {
         panic!("PATH contains invalid character '\"'");
     }
 

Diff for: src/bootstrap/test.rs

@@ -521,7 +521,7 @@ impl Step for RustdocTheme {
     fn make_run(run: RunConfig) {
         let compiler = run.builder.compiler(run.builder.top_stage, run.host);
 
-        run.builder.ensure(RustdocTheme { compiler: compiler });
+        run.builder.ensure(RustdocTheme { compiler });
     }
 
     fn run(self, builder: &Builder) {
@@ -584,9 +584,9 @@ impl Step for RustdocJS {
             });
             builder.run(&mut command);
         } else {
-            builder.info(&format!(
+            builder.info(
                 "No nodejs found, skipping \"src/test/rustdoc-js\" tests"
-            ));
+            );
         }
     }
 }
@@ -653,7 +653,7 @@ impl Step for Tidy {
         }
 
         let _folder = builder.fold_output(|| "tidy");
-        builder.info(&format!("tidy check"));
+        builder.info("tidy check");
         try_run(builder, &mut cmd);
     }
 
@@ -1168,9 +1168,9 @@ impl Step for Compiletest {
             }
         }
         if suite == "run-make-fulldeps" && !builder.config.llvm_enabled {
-            builder.info(&format!(
+            builder.info(
                 "Ignoring run-make test suite as they generally don't work without LLVM"
-            ));
+            );
             return;
         }
 
@@ -1692,10 +1692,10 @@ impl Step for Crate {
             // The javascript shim implements the syscall interface so that test
             // output can be correctly reported.
             if !builder.config.wasm_syscall {
-                builder.info(&format!(
+                builder.info(
                     "Libstd was built without `wasm_syscall` feature enabled: \
                      test output may not be visible."
-                ));
+                );
             }
 
             // On the wasm32-unknown-unknown target we're using LTO which is
@@ -1891,7 +1891,7 @@ impl Step for Distcheck {
 
     /// Run "distcheck", a 'make check' from a tarball
     fn run(self, builder: &Builder) {
-        builder.info(&format!("Distcheck"));
+        builder.info("Distcheck");
         let dir = builder.out.join("tmp").join("distcheck");
         let _ = fs::remove_dir_all(&dir);
         t!(fs::create_dir_all(&dir));
@@ -1919,7 +1919,7 @@ impl Step for Distcheck {
         );
 
         // Now make sure that rust-src has all of libstd's dependencies
-        builder.info(&format!("Distcheck rust-src"));
+        builder.info("Distcheck rust-src");
         let dir = builder.out.join("tmp").join("distcheck-src");
         let _ = fs::remove_dir_all(&dir);
         t!(fs::create_dir_all(&dir));

Diff for: src/bootstrap/tool.rs

@@ -148,7 +148,7 @@ impl Step for ToolBuild {
             }
         });
 
-        if is_expected && duplicates.len() != 0 {
+        if is_expected && !duplicates.is_empty() {
             println!("duplicate artfacts found when compiling a tool, this \
                       typically means that something was recompiled because \
                       a transitive dependency has different features activated \
@@ -170,7 +170,7 @@ impl Step for ToolBuild {
                 println!("    `{}` additionally enabled features {:?} at {:?}",
                          prev.0, &prev_features - &cur_features, prev.1);
             }
-            println!("");
+            println!();
             println!("to fix this you will probably want to edit the local \
                       src/tools/rustc-workspace-hack/Cargo.toml crate, as \
                       that will update the dependency graph to ensure that \
@@ -188,7 +188,7 @@ impl Step for ToolBuild {
             if !is_optional_tool {
                 exit(1);
             } else {
-                return None;
+                None
             }
         } else {
             let cargo_out = builder.cargo_out(compiler, self.mode, target)
@@ -251,7 +251,7 @@ pub fn prepare_tool_cargo(
     if let Some(date) = info.commit_date() {
         cargo.env("CFG_COMMIT_DATE", date);
     }
-    if features.len() > 0 {
+    if !features.is_empty() {
         cargo.arg("--features").arg(&features.join(", "));
     }
     cargo